by right schema i mean have you included samba.schema in your slapd.conf file. This schema defines object attributes and is necessary for smb-ldap.
tail -f will show you the end of a log file in real time as it is being updated. use it on your slapd log and you will almost certainly get some useful information.
tail -f /var/log/slapd.log
If that's not where your slapd log is, check slapd.conf for the path. you may want to add the line "loglevel 512" to your slapd.conf to make your logs more verbose.
Your smb.conf looks fine, but your smbpasswd is using the wrong dn. it dosen't match your directory. Try restarting samba to reload the smb.conf file. If that doesn't work, I don't know. Maybe you accidentally installed samba twice?
SHORTCUT: If you're willing to switch from slackware to fedora core, i know of a script that will completely set up samba with an LDAP backend, create a root account for samba, and give you a working domain in about 5 minutes. It will only run correctly on Fedora Core 3, but it runs great. check out http://majen.net/smbldap/
to get the tarball with the script and all the required rpms. You will probably find this much easier than setting up samba yourself. Just a thought.